The Role of the Endoscopic Endonasal Approach in the Treatment of Trigeminal Schwannomas

Background: Trigeminal schwannomas may require a variety of approaches depending upon their growth pattern. The Endoscopic Endonasal Approach (EEA) provides the additional option of a ventral surgical corridor for the treatment of these tumors.

Objective: To evaluate the role of the EEA in the treatment of trigeminal schwannomas.

Methods: We retrospectively evaluated 16 patients with trigeminal schwannomas, whose treatment consistent of at least one EEA (February, 2004 to August 2014). The clinical, radiological, and pathological information was analyzed.

Results: The average age of the patients was 39 years (20–88), with 12 of 16 being male. Four were recurrent at presentation. The anatomical extension of the tumors dictated the combination of EEA modules used: One tumor involved the pterygopalatine fossa and infratemporal fossa, but did not involve Meckel’s cave. The remainder tumors, all involving Meckel’s cave, extended either to the infratemporal fossa (8 patients), the posterior fossa (6 patients), or the orbit (1 patient). All tumors were WHO Grade 1 except one, which was a Grade 2 (Ki67 1–8%, average 3.6%).

A total of 19 EEAs were performed on 16 patients. Seven patients were managed with a single EEA. Due extensive tumors, one patient had a simultaneous combined EEA, Caldwell-Luc, and transcervical approach, and four others had planned staged approaches (one patient had three EEA stages, whereas three others had EEAs combined with lateral approaches). The remainder four other patients had more than one procedure, but those were not performed in a planned staged manner: one patient had two EEAs, whereas three other patients had one EEA in addition to open approaches.

Gross total resection with the EEA was achieved in 9 of 11 cases in which this was the goal of surgery. In two of these cases a small residual was left to avoid the risk of nerve or vascular injury. A planned sub-total resection for symptom control was performed in the remainder 5 patients, either because of extensive bleeding in giant tumors (2 cases), or to avoid nerve or vascular injuries (3 cases). After a mean follow-up of 46.2 months, three tumors recurred and required further treatment. The remainder patients were either disease free (7 patients) or had a stable residual on serial imaging (6 patients). At their last clinical follow-up, nine patients experienced improvement in their pre-operative symptoms; four remained unchanged, whereas three patients experienced improvement in some symptoms in exchange for trigeminal dysfunction. With regards to complications: one patient experienced a postoperative cerebrospinal fluid leak requiring re-exploration, one patient had a severe intra-operative transfusion reaction, and another patient had a carotid injury. The latter was treated endoscopically with an aneurysm clip, with only insignificant stenosis of the parent vessel and no sequelae.

Conclusions: The ventral surgical corridor of the EEA is a useful adjunct to microsurgery and radiosurgery for the treatment of trigeminal schwannomas. In selected cases it can be a safe and effective stand-alone approach.